Introduction

The light of the point light source is diffused outward in the shape of a sphere. As the diffusion distance increases, the amount of light energy per unit surface area of the sphere becomes smaller and smaller.

How to calculate the light energy?

Calculate

GAMES 101

In the figure, the unit light energy of a sphere at radius 1 is set to I1I_1, and at radius r is set to I2I_2.

According to the law of conservation of energy, the total energy is constant. So we get the equation

I14π12=I24πr2I2=I14π4πr2I2=I1r2 I_1 4\pi 1^2 = I_24\pi r^2 \\[5px] I_2 = \frac{I_14\pi}{4\pi r^2} \\[5px] I_2 = \frac{I_1}{r^2}

References

GAMES 101-現代計算機圖形學入門-闫令琪